1. Field
The present specification generally relates to pulling rolls for use in the manufacture of sheet glass in a glass manufacturing process.
2. Technical Background
Pulling rolls are used in the manufacture of sheet glass to apply a vertical pulling force to a ribbon or web of glass from which individual sheets are formed. The amount of pulling force applied by the pulling rolls to the glass is utilized to control the nominal thickness of the glass as the glass is drawn from molten glass, such as in an overflow downdraw fusion process, as described in U.S. Pat. Nos. 3,338,696 and 3,682,609, or a similar process. In addition to a main pulling roll, additional rolls are sometimes used in ribbon drawing processes to stabilize ribbon motion, or to create horizontal tension across the glass ribbon. Though generically referred to as pulling rolls, these rolls can sometimes be run without drive motors so that the rolls turn because of the contact with the moving glass ribbon. Whether driven or idled, rolls which contact the ribbon during the drawing process are referred to as pulling rolls.
Pulling rolls are generally designed to contact the glass web at its outer edges, usually in an area just inboard of the thickened beads that form at the very edges of the glass ribbon. An important aspect of roll function is to avoid cracking of the ribbon which can cause process outages and restarts. Because the pulling rolls are in direct contact with the surface of the glass ribbon, damage to the surface of the glass occurs from contact with the pulling rolls. In addition, tramp glass particles can become embedded in the surface of the pulling roll resulting in additional damage to the glass as the pulling rolls contact the glass.
Accordingly, alternative pulling roll designs are needed.